Which factions should I ally with and which should I punch into the sun with my glorious unarmed cyborg?
As far as I remember, The Followers of the Apocalypse are cool, The Kings are funny and the NCR are lame military neolibs that use prison labour.
Oh, and I'm curbstomping Caesar the first chance I get.
As far as the main quest goes, you can't really do anything with the Followers, and the only thing you can do with the Kings is broker a treaty with the NCR if you're doing the NCR route.
I usually do:
Foil the Omertas
Expose the White Gloves
Convince the Khans to suicide attack the dam
Destroy the Brotherhood
Ally the Boomers